It is well known to incorporate a light-reflective pigment in a photographic element. For example, Japanese Patent Application (OPI) No. 17435/83 (the term "OPI" used herein refers to an "unexamined published application") discloses incorporation of a light-reflective pigment, e.g., titanium oxide, in a layer adjacent to a silver halide emulsion layer (i.e., a backing layer) for the purpose of increasing sensitivity through control of light at the time of exposure. Further, use of pearlescent pigments in place of titanium oxide for the same purpose is disclosed in Japanese Patent Publication Nos. 3406/79, 6172/76, and 49174/74.
Light-reflective pigments have been employed not only for improvement of sensitivity as mentioned above, but also for construction of a light-reflective layer serving as the background of an image (also referred to as a background layer).
Although titanium dioxide, magnesium sulfate, zinc oxide, zirconium oxide, aluminum oxide and zinc carbonate used for these purposes are superior in light reflectivity, they involve problems such as unstable supply because they are mineral resources and impairment of photographic properties, for example, by accelerating light discoloration of image-forming dyes, due to their photochemical activity.
Accordingly, it has been desired to develop a light-reflective material as a substitute for such photochemically active light-reflective pigments, viz., a photochemically inactive material which is not inferior to titanium oxide.
Further, when the conventionally employed titanium oxide is mixed with a binder, such as gelatin and polyvinyl alcohol, flocculation frequently occurs unless high energy is applied by a dispersing machine, etc., which gives rise to great difficulty in production control. Development of a light-reflective material in place of titanium dioxide is significant also from this point of view.
In monosheet type photographic light-sensitive elements, titanium dioxide, etc., are inexpensive and also excellent in light reflectivity as light-reflective pigments. However, they must be used in a large quantity for forming a background of a transferred image, thus necessarily resulting in large film thickness. As a result, it takes time for the image-forming materials to penetrate through a white reflective layer, thereby retarding image formation. In this sense, it has been desired to make a white reflective layer as thin as possible.
From the viewpoint of filing photographic prints typically inserted into albums, monosheet type photographic light-sensitive elements are inconvenient due to their thickness. A method for eliminating this inconvenience is disclosed in Japanese Patent Application (OPI) Nos. 67840/81 and 220727/84, etc. According to this method, after a monosheet photographic light-sensitive material is exposed to light and developmentprocessed, an image-receiving element including a white reflective layer (i.e., photographic print) is stripped from a light-sensitive element to thereby make the photographic print thinner.
However, a light-sensitive element of this type, as disclosed in Japanese Patent Application No. 220727/84, requires two additional hydrophilic polymer layers in order to facilitate stripping, leading to a great increase of film thickness, thus involving a serious problem such that transfer of image-forming materials to an image-receiving layer, i.e., image-formation is retarded.
It has been described to use a hydrophobic compound, such as straight chain alkyl group perfluoroalkylate sulfonamide esters, polyethylene oxide perfluoroalkylate sulfonamide esters, etc., as the aforesaid stripping layer instead of the hydrophilic polymer, as disclosed in U.S. Pat. No. 4,459,346. This method, however, similarly requires an extra layer which functions only for stripping, and which, therefore, has many disadvantages, such as increasing costs and necessitating equipment for coating such a layer.
Hence, the present inventors have conducted investigations in an attempt to develop a photochemically inactive light-reflective material as a substitute for photochemically active light-reflective pigments, such as titanium dioxide, and further to develop a light-reflective material providing a white reflective layer (background layer) which also serves as a stripping layer.